This invention relates to the transfer of graphical information and, more particularly, to a method and apparatus utilizing magnetic storage for transferring graphical information.
In photocopying, graphical information is transferred from an original medium to a copy medium one or a number of times depending upon the number of copies desired. Many prior art photocopying processes include optical scanning of the original to create an electrostatic image on a surface, such as the surface of a drum or a plate having a layer of photoconductive insulating material affixed to a conductive backing for supporting electrostatic images. The surface is electrostatically charged and then exposed to a light pattern of the image being reproduced. The electrostatic image thus formed is developed by applying to the surface a powder known as toner which is attracted to the electrostatic image to produce a visible powder image. Then the particles are transferred and fixed to a copy medium such as paper in correspondence with the visible image.
A significant problem with present photocopying methods and apparatus is the volatility of the image formed therein, in other words the image is lost in the transfer step to the copying medium. An immediate consequence is the need to successively scan the original and form another image for each copy to be made. In addition to increasing the complexity and cost of the apparatus, this limits the speed of operation when a number of copies are to be made. Furthermore, this also requires that the original be retained in the apparatus for the duration of the copying operation which may be undesirable when a large number of copies is to be made. Another problem with many present photocopying methods and arrangements is the need to use a particular kind or otherwise specially treated paper for the copies as opposed to readily available ordinary types of paper.
In recent times there has developed an increasing need for apparatus capable of reversably transferring graphical information from a conventional hard copy to and from a computer for storage and/or processing. The interface of graphical information with computer usage requires optical scanning of the hard copy, electronic processing of the electrical output information and final storage of this information in the computer system.
Apparatus heretofore available is extremely expensive and complex, such as known arrangements including cathode ray tubes and associated systems, in addition to lacking flexibility in many instances.